In the aerospace industry there is a need for structures able to withstand mechanical impact and several proposals thereof are known. For example, the document ES 2 398 287 A1 describes an impact resistant and damage tolerant fuselage part comprising a skin, a plurality of frames arranged perpendicular to the longitudinal axis of the fuselage and also an upper longitudinal box, with or without internal divisions, and a bottom longitudinal box, with or without internal divisions, that are configured to form together with the skin, a multi-cell structure, belonging in each cell the outer side to the skin and the inner sides to the longitudinal boxes. The part also comprises a plurality of lateral beams which are interconnected with the frames to form a structural unit with the skin. The components are dimensioned so that the aircraft can cope with, for example, mechanical impacts from detached parts of aircraft engines to maintain a sufficient number of closed cells.
As for noise impacts, ES 2 211 586 A1 discloses the use of micro-perforated panels (MPP's) for skins in transportation means such as cars, trains, boats and planes. They are panels of thickness t in the range 0.2≤t≤5 mm, perforation diameter d in the range 0.05≤d≤2 mm, and perforation percentages in the range p 0.2≤p≤4%. The air cavity, in this case, may be filled with foam or wadding.
Thus, the solutions proposed in the prior art to address mechanical and acoustic impacts are very different. However structurally similar solutions for both types of impacts are desirable.